Ben chose not to stand for reelection in 1842 but returned to surveying and the pursuit of a quasimilitary career. At the battle of Plum Creek on August 12, 1840, he distinguished himself as a scout and as commander of the right wing of the Texas army. In February 1842, when the Mexican government launched a raid against Texas that seized the strategic town of San Antonio, McCulloch rendered invaluable service by scouting enemy positions and taking a prominent role in the fighting that harried Rafael Vásquez's raiders back below the Rio Grande. On September 11, 1842, a second Mexican expedition captured San Antonio. McCulloch again did valuable scouting service and joined in the pursuit of Adrián Woll's invading troops to the Hondo River, where Hays's rangers engaged them on September 21. After the repulse of the second Mexican invasion, McCulloch remained with the ranger company that formed the nucleus of an army with which the Texans planned to invade Mexico. The so-called Somervell expedition was poorly managed, however, and Ben and Henry left it on the Rio Grande only hours before the remainder of the Texans were captured at Mier, Tamaulipas, on December 25, 1842. McCulloch was elected to the First Legislature after the annexation of Texas.
At the outbreak of the Mexican War he raised a command of Texas Rangers that became Company A of Col. Jack Hays's First Regiment, Texas Mounted Volunteers. He was ordered to report to the United States Army on the Rio Grande and was soon named Zachary Taylor's chief of scouts. As such he won his commander's praise and the admiration of the nation with his exciting reconnaissance expeditions into northern Mexico. The presence in his company of George Wilkins Kendall, editor of the New Orleans Picayune, and Samuel Reid, who later wrote a popular history of the campaign, The Scouting Expeditions of McCulloch's Texas Rangers, propelled McCulloch's name into national prominence. Leading his company as mounted infantry at the battle of Monterrey, McCulloch further distinguished himself, and before the battle of Buena Vista his astute and daring reconnaissance work saved Taylor's army from disaster and won him a promotion to the rank of major of United States volunteers.
McCulloch returned to Texas at the end of the war, served for a time as a scout under Bvt. Maj. Gen. David E. Twiggs, and traveled to Tennessee on family business before setting out from Austin on September 9, 1849, for the gold fields of California. Although he failed to strike it rich, he was elected sheriff of Sacramento. His friends in the Senate, Sam Houston and Thomas Jefferson Rusk, mounted a campaign to put him in command of a regiment of United States cavalry for duty on the Texas frontier, but largely due to McCulloch's lack of formal education the attempt was frustrated. In 1852 President Franklin Pierce promised him the command of the elite Second United States Cavalry, but Secretary of War Jefferson Davis bestowed the command instead on his personal favorite, Albert Sidney Johnston. McCulloch was, however, appointed United States marshal for the Eastern District of Texas and served under Judge John Charles Watrous during the administrations of Franklin Pierce and James Buchanan. In 1858 he was appointed one of two peace commissioners to treat with Brigham Young and the elders of the Mormon Church; he is credited with helping to prevent armed hostilities between the United States government and the Latter-Day Saints in Utah.
When secession came to Texas, McCulloch was commissioned a colonel and authorized to demand the surrender of all federal posts in the Military District of Texas. After a bloodless confrontation at the Alamo on February 16, 1861, General Twiggs turned over to McCulloch the federal arsenal and all other United States property in San Antonio. On May 11, 1861, Jefferson Davis appointed McCulloch a brigadier general, the second-ranking brigadier general in the Confederate Army and the first general-grade officer to be commissioned from the civilian community. McCulloch was assigned to the command of Indian Territory and established his headquarters at Little Rock, Arkansas, where he began to build the Army of the West with regiments from Arkansas, Louisiana, and Texas. Although hampered by logistical nightmares and a total disagreement over strategic objectives with Missouri general Sterling Price, with whom he had been ordered to cooperate, McCulloch, with the assistance of Albert Pike, established vital alliances with the Cherokees, Choctaws, Creeks, and other inhabitants of what is now eastern Oklahoma. On August 10, 1861, he won an impressive victory over the army of Brig. Gen. Nathaniel Lyon at Wilson's Creek, or Oak Hills, in southwest Missouri. McCulloch's continuing inability to come to personal or strategic accord with Price, however, caused President Davis, on January 10, 1862, to appoint Maj. Gen. Earl Van Dorn to the command of both McCulloch's and Price's armies. Van Dorn launched the Army of the West on an expedition to capture St. Louis, a plan that McCulloch bitterly resisted. The Confederates encountered the army of Union major general Samuel R. Curtis on the Little Sugar Creek in northwest Arkansas. Due largely to McCulloch's remarkable knowledge of the terrain, Van Dorn's army was able to flank the enemy out of a strong position and cut his line of communication to the north. McCulloch, commanding the Confederate right wing in the ensuing battle of Pea Ridge, or Elkhorn Tavern, on March 7, 1862, overran a battery of artillery and drove the enemy from his original position. As federal resistance stiffened around 10:30 A.M., however, McCulloch rode forward through the thick underbrush to determine the location of the enemy line, was shot from his horse, and died instantly. His command devolved upon Brig. Gen. James M. McIntosh, who was killed but a few minutes later while leading a charge to recover McCulloch's body. Col. Louis Hébert, the division's senior regimental commander, was captured in the same charge, and soon McCulloch's division, without leadership, began to fall apart and drift toward the rear. Most participants and later historians attribute to McCulloch's untimely death the disaster at Pea Ridge and the subsequent loss of Arkansas to the Union forces.
McCulloch was first buried on the field, but his body was removed to the cemetery at Little Rock and thence to the State Cemetery in Austin. McCulloch never married. His papers are located in the Barker Texas History Center at the University of Texas at Austin. Source
30° 15.921, -097° 43.636
Texas State Cemetery